Initial CSI basin planning, 1999-2003
South Green River planning area
The South Green River Planning Area includes the King County wastewater service area south of the county's Kent-Cross Valley facility. This area is divided into three planning zones covering basically the City of Kent, the City of Auburn (including the City of Pacific), and the southern part of the Soos Creek Water and Sewer District service area (which includes Black Diamond).
Planning was completed for this area early in 2001 and the county continued to coordinate with local sewer agencies in south King County to detail needed conveyance improvements in both the regional and local conveyance systems. This plan optimizes the use of both King County and local wastewater facilities.
The following commitments with the Soos Creek Water and Sewer District achieve King County's goals for sewer improvements in the Soos Planning Zone and ensure that the improvements benefit the widest possible area and the greatest number of ratepayers.
- Design, construct, and operate three new pumping stations and approximately 10 miles of sewer pipeline in this area
- Design, construct, and operate an interceptor running from the existing Black Diamond trunk sewer near SR-516 to a new pump station
- Cooperate with the District in developing and operating existing and planned regional facilities
- Eventually convey Black Diamond flows entirely through King County facilities
The current working alternative for the Kent and Auburn Planning Zones calls for a separate pipeline near the West Valley Highway called the Southwest Interceptor. This pipe would divert flow from south Auburn around the Auburn Interceptor and relieve the capacity problems in the existing line. A number of minor connection/diversion projects are then necessary to bring wastewater flow to the Southwest Interceptor.
The Wastewater Treatment Division is looking into alternatives to reduce the cost of these upgrades by phasing the needed improvements. These working alternatives were reviewed based on the latest population and employment data and the recently calibrated infiltration and inflow models. Findings of this review include, for example, that all modeling and sizing calculations for CSI planning work are based on the assumption that surcharge at County manholes is not acceptable. Allowing limited amounts of surcharging may enable the County to postpone or eliminate some elements of the working alternative for the Kent and Auburn portions of the South Green River planning area. The systems in this area currently surcharge during significant storm events. Limited surcharging may be a viable system operating condition during storm events in the future.
This three-part report describes specific conveyance system issues related to capacity limitations; existing and proposed facilities within the South Green River Planning Area; characterization of the physical and natural environment, known sensitive areas, and the general natural resources located in the planning area.
South Green River: Existing Conditions (Mill Creek/Green River Subregional Planning Area), February 2000
Title Page and Table of Contents
Task 210: Planning Record Summary (2.8 MB)
Task 220: Existing Facilities (72 KB)
Task 230: Existing Conditions (1.4 MB) |
South Green River Planning Area: Alternatives Analysis, (Task 240), June 2001 (1.5 MB)
Development of alternatives to provide sewer service to the South Green River Planning Area which includes all of King County's wastewater service area south of Kent as described in this report.
Figures and appendices are listed separately:
Figures 2 - 5 (716 KB)
Figures 6 - 9 (792 KB)
Figures 10 - 13 (828 KB)
Figures 14 -17 (904 KB)
Appendices A - I (3.1 MB) |
South Green River Planning Area: Working Alternative Refinement, (Task 250), June 2001 (4.9 MB)
This report compares the alternatives proposed to provide regional wastewater service to the South Green River Planning Area through the year 2050, as described in the Alternatives Analysis Report. |
South Green River Planning Area: Working Alternative Refinement Kent & Auburn Planning Zones, (Task 250 Final Supplemental Report), June 2001 (2.9 MB)
Additional development and evaluation of the most advantageous alternatives in the Kent and Auburn planning zones is presented in this supplement. |
South Green River Planning Area: Working Alternative Refinement Supplement, Kent & Auburn Planning Zones, Cost and Phasing (Task 250A Supplemental Report), December 2003 (5 MB)
This report investigates ways to reduce cost of working alternatives upgrades by phasing the needed improvements.
Table of Contents |
South Green River Subregional Area: Working Alternative Refinement (Supplement) Soos Planning Zone, (Task 250A Supplemental Report), July 2001 (1.9 MB)
Additional development and evaluation of the Soos planning zone working alternative is presented in this supplement. |
South Green River Subregional Area: Working Alternative Refinement (Supplement) 3A, Soos Planning Zone, May 2002 (3.5 MB)
This supplemental report describes additional engineering planning level analysis performed for the Soos planning zone.
Appendix A (380 KB)
Appendix B (464 KB) |
South Green River Subregional Area Planning Area Summary Report, July 2001 (372 KB)
This summary of the CSI Project team's work in the South Green River Planning Area outlines working alternatives for addressing wastewater conveyance issues in the planning area.
Figures are listed separately:
Figures 1 - 5 (2.1 MB) |
Pacific Pump Station Pacific Pump Station, December 1999 (676 KB)
This study evaluates the County's existing Pacific Pump Station, located within the City of Pacific, and related conveyance system components, and identifies improvements needed to convey the projected increasing basin flows. |
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